How to Implement the javascript FormatNumber Function

Since javascript does not have this function, how can we implement it? The following figure shows the function: <script language = javascript src = "formatnumber. javaScript "> </script> can be added to your html page.
<! -- # Include file = "formatnumber. js" --> Add your asp page; or use
<? Include ("formatnumber. js")?> Add to the php page; or use
<% @ # Include file = "formatnumber. js" %> Add to the jsp page.
This formatnumber sub-function is as follows:
<Script language = javascript>
<! --
Function formatnumber (srcstr, nafterdot ){
Var srcstr, nafterdot;
Var resultstr, nten;
Srcstr = "" + srcstr + "";
Strlen = srcstr. length;
Dotpos = srcstr. indexof (".", 0 );
If (dotpos =-1 ){
Resultstr = srcstr + ".";
For (I = 0; I <nafterdot; I ++ ){
Resultstr = resultstr + "0 ";
}
Return resultstr;
}
Else {
If (strlen-dotpos-1)> = nafterdot ){
Nafter = dotpos + nafterdot + 1;
Nten = 1;
For (j = 0; j <nafterdot; j ++ ){
Nten = nten * 10;
}
Resultstr = math. round (parsefloat (srcstr) * nten)/nten;
Return resultstr;
}
Else {
Resultstr = srcstr;
For (I = 0; I <(nafterdot-strlen + dotpos + 1); I ++ ){
Resultstr = resultstr + "0 ";
}
Return resultstr;
}
}
}